A seatbelt system is one type of safety system used in vehicles today to prevent or reduce vehicle occupant injury during a vehicle collision. Typically, the seatbelt system includes seatbelt webbing that is stored in a retractor when not in use and protracted from the retractor and secured around the vehicle occupant when in use. The retractor includes a spring for retracting the seatbelt webbing from the retractor. The webbing is wound around a spool or spindle. If the retractor is a load limiting retractor the spindle is coupled to a torsion bar. During normal use and when the vehicle is not involved in the vehicle collision, the spindle freely rotates when the webbing is retracted or protracted from the retractor. However, during a vehicle collision, the seatbelt webbing must be prevented from protracting from the retractor in order to restrain the vehicle occupant's movement toward the vehicle interior. A locking mechanism is provided in the retractor to prevent further protraction of the seatbelt webbing by preventing the one end of the torsion bar and spindle from rotating.
During a vehicle impact and when the spool and torsion bar are rotationally locked, it is desirable to “pay out” some portion of the seatbelt webbing to prevent peak loading on the vehicle occupant. Thus, the torsion bar provides the desired “pay out” feature by twisting a predetermined amount during vehicle impact allowing the seatbelt webbing to “payout.” A further enhancement to seatbelt retractors is a torsion bar that allows multiple levels of load limiting. The multiple levels of load limiting are achieved through the use of a multi-segmented torsion bar. Current multi-segmented torsion bars are designed to prevent interference with the seatbelt webbing which is routed through the spool and past the torsion bar. This is achieved in conventional retractors by designing the segments between splines to be no shorter than the width of the seatbelt webbing. If the webbing does not pass over the spline, a supplemental sleeve or spacer may be used. Thus, the size and packaging of the seatbelt retractor are significantly constrained either by width of the seatbelt retractor or diameter of the spindle.
Therefore, a need exists for a new and improved seatbelt retractor that provides a multiple load-limiting feature and is able to be packaged in smaller retractors. Further, the seatbelt webbing of the new and improved retractor should not interfere with the multiple load-limiting torsion bar and be capable of installation through the retractor spindle with supplemental components.